Directive window ablation antenna with dielectric loading

ABSTRACT

An electrosurgical device for directing energy to a target volume of tissue includes a coaxial feedline having an inner conductor, an outer conductor coaxially disposed around the inner conductor, and a dielectric material disposed therebetween. An elongated electrically-conductive member is longitudinally disposed at a distal end of the inner conductor. A balun structure is disposed on the outer conductor. The device also includes an electrically-conductive cylinder coaxially disposed around a distal portion of the balun structure, and a dielectric structure disposed substantially adjacent to a distal end of the electrically-conductive cylinder, wherein the dielectric structure longitudinally extends from the distal end of the electrically-conductive cylinder to a distal end of the electrically-conductive member.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation application, which claimspriority to, and the benefit of, U.S. patent application Ser. No.12/535,856, filed on Aug. 5, 2009, the disclosure of which is hereinincorporated by reference in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to electrosurgical devices suitable foruse in tissue ablation applications and, more particularly, toelectrosurgical devices with directional radiation patterns.

2. Discussion of Related Art

Treatment of certain diseases requires the destruction of malignanttissue growths, e.g., tumors. Electromagnetic radiation can be used toheat and destroy tumor cells. Treatment may involve inserting ablationprobes into tissues where cancerous tumors have been identified. Oncethe probes are positioned, electromagnetic energy is passed through theprobes into surrounding tissue.

In the treatment of diseases such as cancer, certain types of tumorcells have been found to denature at elevated temperatures that areslightly lower than temperatures normally injurious to healthy cells.Known treatment methods, such as hyperthermia therapy, heat diseasedcells to temperatures above 41° C. while maintaining adjacent healthycells below the temperature at which irreversible cell destructionoccurs. These methods involve applying electromagnetic radiation toheat, ablate and/or coagulate tissue. Microwave energy is sometimesutilized to perform these methods. Other procedures utilizingelectromagnetic radiation to heat tissue also include coagulation,cutting and/or ablation of tissue.

Electrosurgical devices utilizing electromagnetic radiation have beendeveloped for a variety of uses and applications. A number of devicesare available that can be used to provide high bursts of energy forshort periods of time to achieve cutting and coagulative effects onvarious tissues. There are a number of different types of apparatus thatcan be used to perform ablation procedures. Typically, microwaveapparatus for use in ablation procedures include a microwave generatorthat functions as an energy source, and a microwave surgical instrument(e.g., microwave ablation probe) having an antenna assembly fordirecting the energy to the target tissue. The microwave generator andsurgical instrument are typically operatively coupled by a cableassembly having a plurality of conductors for transmitting microwaveenergy from the generator to the instrument, and for communicatingcontrol, feedback and identification signals between the instrument andthe generator.

There are several types of microwave antenna assemblies in use, e.g.,monopole, dipole and helical, which may be used in tissue ablationapplications. In monopole and dipole antenna assemblies, microwaveenergy generally radiates perpendicularly away from the axis of theconductor. Monopole antenna assemblies typically include a single,elongated conductor. A typical dipole antenna assembly includes twoelongated conductors, which are linearly aligned and positionedend-to-end relative to one another with an electrical insulator placedtherebetween. Helical antenna assemblies include a helically-shapedconductor connected to a ground plane. Helical antenna assemblies canoperate in a number of modes including normal mode (broadside), in whichthe field radiated by the helix is maximum in a perpendicular plane tothe helix axis, and axial mode (end fire), in which maximum radiation isalong the helix axis.

A microwave transmission line typically includes a thin inner conductorthat extends along the longitudinal axis of the transmission line and issurrounded by a dielectric material and is further surrounded by anouter conductor around the dielectric material such that the outerconductor also extends along the transmission line axis. In onevariation of an antenna, a waveguiding structure, e.g., a length oftransmission line or coaxial cable, is provided with a plurality ofopenings through which energy “leaks” or radiates away from the guidingstructure. This type of construction is typically referred to as a“leaky coaxial” or “leaky wave” antenna.

Some ablation targeted lesions are too small or too hard to be puncturedby an ablation probe. In these cases, doctors may place the probe asclose as possible to the lesion and perform an ablation. Withnon-directional ablation probes, the ablation may radiate to both sidesof the probe which may damage healthy tissue located on the non-tumorside of the radiating section.

During certain procedures, it can be difficult to assess the extent towhich the microwave energy will radiate into the surrounding tissue,making it difficult to determine the area or volume of surroundingtissue that will be ablated.

SUMMARY

The present disclosure relates to a device for directing energy to atarget volume of tissue including a coaxial feedline having an innerconductor, an outer conductor coaxially disposed around the innerconductor, and a dielectric material disposed therebetween. An elongatedelectrically-conductive member is longitudinally disposed at a distalend of the inner conductor. A balun structure is disposed on the outerconductor. The device includes an electrically-conductive cylindercoaxially disposed around a distal portion of the balun structure. Thedevice also includes a dielectric structure disposed substantiallyadjacent to a distal end of the electrically-conductive cylinder,wherein the dielectric structure longitudinally extends from the distalend of the electrically-conductive cylinder to a distal end of theelectrically-conductive member.

The present disclosure also relates to a method for manufacturing anelectrosurgical device including the step of providing a coaxialfeedline having an inner conductor, an outer conductor, and a dielectricmaterial disposed therebetween, and joining an electrically-conductivemember to a distal end of the inner conductor at a distal end of thecoaxial feedline. The method also includes the steps of: forming adielectric layer around a distal portion of the outer conductor; formingan electrically-conductive layer around a proximal portion of thedielectric layer such that the electrically-conductive layer iselectrically coupled to the outer conductor; joining anelectrically-conductive cylinder to distal portion of theelectrically-conductive layer; and forming a dielectric structuredisposed substantially adjacent to a distal end of theelectrically-conductive cylinder, wherein the dielectric structurelongitudinally extends from the distal end of theelectrically-conductive cylinder to a distal end of theelectrically-conductive member.

BRIEF DESCRIPTION OF THE DRAWINGS

Objects and features of the presently disclosed antenna assemblies willbecome apparent to those of ordinary skill in the art when descriptionsof various embodiments thereof are read with reference to theaccompanying drawings, of which:

FIG. 1 is a schematic diagram of an ablation system according to anembodiment of the present disclosure;

FIG. 2 is a perspective view with parts separated of a portion of anenergy applicator according to an embodiment of the present disclosure;

FIG. 3 is a perspective, assembled view of the portion of the energyapplicator of FIG. 2 shown with a dielectric layer disposed about aportion of the outer conductor according to an embodiment of the presentdisclosure;

FIG. 4 is a perspective view of the portion of the energy applicator ofFIG. 3 shown with an electrically-conductive layer disposed about aportion of the dielectric layer according to an embodiment of thepresent disclosure;

FIG. 5 is a perspective view of the portion of the energy applicator ofFIG. 4 shown with an electrically-conductive cylinder disposed about thedistal end of the electrically-conductive layer according to anembodiment of the present disclosure;

FIG. 6 is a perspective view of the portion of the energy applicator ofFIG. 3 shown with another embodiment of an electrically-conductive layerand an electrically-conductive cylinder according to the presentdisclosure;

FIG. 7 is an enlarged view of the indicated area of detail of FIG. 6according to an embodiment of the present disclosure;

FIG. 8 is a perspective view of the portion of the energy applicator ofFIG. 5 shown with a dielectric structure disposed distal to theelectrically-conductive cylinder according to an embodiment of thepresent disclosure;

FIG. 9 is a perspective view of the portion of the energy applicator ofFIG. 8 shown with a fluid inflow tube and a fluid outflow tube accordingto an embodiment of the present disclosure;

FIG. 10 is an enlarged view of the indicated area of detail of FIG. 9according to an embodiment of the present disclosure;

FIG. 11A is a perspective view of the portion of the energy applicatorof FIG. 8 shown with a sleeve member surrounding a distal portion of theenergy applicator according to an embodiment of the present disclosure;

FIG. 11B is a perspective view of the portion of the energy applicatorof FIG. 9 shown with a sleeve member surrounding a distal portion of theenergy applicator according to an embodiment of the present disclosure;

FIG. 12A is a perspective view of the portion of the energy applicatorof FIG. 11A shown with an end member coupled to the distal end of thesleeve member according to an embodiment of the present disclosure;

FIG. 12B is a perspective view of the portion of the energy applicatorof FIG. 11B shown with an end member coupled to the distal end of thesleeve member according to an embodiment of the present disclosure;

FIG. 13A is a perspective view of the portion of the energy applicatorof FIG. 12A shown with a longitudinal chamber disposed between theelectrically-conductive cylinder and the end member according to anembodiment of the present disclosure;

FIG. 13B is a perspective view of the portion of the energy applicatorof FIG. 12B shown with a longitudinal chamber disposed between theelectrically-conductive cylinder and the end member according to anembodiment of the present disclosure;

FIG. 14 is a perspective view of the portion of the energy applicator ofFIG. 13A shown with a material layer disposed in an outer portion of thewindow according to an embodiment of the present disclosure;

FIG. 15 is a cross-sectional view of an energy applicator shown with adiagrammatic representation of an emitted radiation pattern according toan embodiment of the present disclosure;

FIG. 16 is a cross-sectional view of another embodiment of an energyapplicator shown with a diagrammatic representation of an emittedradiation pattern according to the present disclosure;

FIG. 17 is a diagrammatic representation of a radiation pattern ofelectromagnetic energy delivered into tissue by an energy applicator,such as the energy applicator of FIG. 14, according to an embodiment ofthe present disclosure;

FIG. 18 is a cross-sectional view of an energy applicator shown with adiagrammatic representation of an emitted radiation pattern according toan embodiment of the present disclosure;

FIG. 19 is a cross-sectional view of another embodiment of an energyapplicator shown with a diagrammatic representation of an emittedradiation pattern according to the present disclosure;

FIG. 20 is a cross-sectional view of yet another embodiment of an energyapplicator shown with a diagrammatic representation of an emittedradiation pattern according to the present disclosure; and

FIG. 21 is a flowchart illustrating a method of manufacturing anelectrosurgical device according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION

Hereinafter, embodiments of the presently disclosed electrosurgicaldevice with a directional radiation pattern will be described withreference to the accompanying drawings. Like reference numerals mayrefer to similar or identical elements throughout the description of thefigures. As shown in the drawings and as used in this description, andas is traditional when referring to relative positioning on an object,the term “proximal” refers to that portion of the apparatus that iscloser to the user and the term “distal” refers to that portion of theapparatus that is further from the user.

Electromagnetic energy is generally classified by increasing energy ordecreasing wavelength into radio waves, microwaves, infrared, visiblelight, ultraviolet, X-rays and gamma-rays. As it is used in thisdescription, “microwave” generally refers to electromagnetic waves inthe frequency range of 300 megahertz (MHz) (3×10⁸ cycles/second) to 300gigahertz (GHz) (3×10¹¹ cycles/second). As it is used in thisdescription, “ablation procedure” generally refers to any ablationprocedure, such as microwave ablation, radio frequency (RF) ablation ormicrowave ablation assisted resection. As it is used in thisdescription, “transmission line” generally refers to any transmissionmedium that can be used for the propagation of signals from one point toanother.

Various embodiments of the present disclosure provide electrosurgicaldevices for treating tissue and methods of directing electromagneticradiation to a target volume of tissue. Embodiments may be implementedusing electromagnetic radiation at microwave frequencies or at otherfrequencies. An electrosurgical system including an energy applicator,according to various embodiments, is designed and configured to operatebetween about 500 MHz and about 10 GHz with a directional radiationpattern.

Various embodiments of the presently disclosed electrosurgical devicewith a directional radiation pattern are suitable for microwave ablationand for use to pre-coagulate tissue for microwave ablation assistedsurgical resection. Although various methods described hereinbelow aretargeted toward microwave ablation and the complete destruction oftarget tissue, it is to be understood that methods for directingelectromagnetic radiation may be used with other therapies in which thetarget tissue is partially destroyed or damaged, such as, for example,to prevent the conduction of electrical impulses within heart tissue. Inaddition, although the following description describes the use of adipole microwave antenna, the teachings of the present disclosure mayalso apply to a monopole, helical, or other suitable type of microwaveantenna.

FIG. 1 shows an electrosurgical system 10 according to an embodiment ofthe present disclosure that includes an energy applicator or probe 100.Probe 100 generally includes an antenna assembly 12 having a radiatingportion connected by a feedline 110 (or shaft) via a transmission line15 to a connector 16, which may further operably connect the probe 100to an electrosurgical power generating source 28, e.g., a microwave orRF electrosurgical generator.

Feedline 110 may be formed from a suitable flexible, semi-rigid or rigidmicrowave conductive cable and may connect directly to anelectrosurgical power generating source 28. Alternatively, the feedline110 may electrically connect the antenna assembly 12 via thetransmission line 15 to the electrosurgical power generating source 28.Feedline 110 may have a variable length from a proximal end of theantenna assembly 12 to a distal end of transmission line 15 ranging froma length of about one inch to about twelve inches. Feedline 110 may beformed of suitable electrically conductive materials, e.g., copper,gold, silver or other conductive metals having similar conductivityvalues. Feedline 110 may be made of stainless steel, which generallyoffers the strength required to puncture tissue and/or skin. Conductivematerials used to form the feedline 110 may be plated with othermaterials, e.g., other conductive materials, such as gold or silver, toimprove their properties, e.g., to improve conductivity, decrease energyloss, etc. In some embodiments, the feedline 110 includes stainlesssteel, and to improve the conductivity thereof, the stainless steel maybe coated with a layer of a conductive material such as copper or gold.Feedline 110 may include an inner conductor, a dielectric materialcoaxially surrounding the inner conductor, and an outer conductorcoaxially surrounding the dielectric material. Antenna assembly 12 maybe formed from a portion of the inner conductor that extends distal ofthe feedline 110 into the antenna assembly 12. Feedline 110 may becooled by fluid e.g., saline or water, to improve power handling, andmay include a stainless steel catheter.

In some embodiments, the power generating source 28 is configured toprovide microwave energy at an operational frequency from about 500 MHzto about 2500 MHz. In other embodiments, the power generating source 28is configured to provide microwave energy at an operational frequencyfrom about 500 MHz to about 10 GHz. Power generating source 28 may beconfigured to provide various frequencies of electromagnetic energy.Transmission line 15 may additionally, or alternatively, provide aconduit (not shown) configured to provide coolant from a coolant source18 to the probe 100.

Located at the distal end of the antenna assembly 12 is an end cap ortapered portion 120, which may terminate in a sharp tip 123 to allow forinsertion into tissue with minimal resistance. The end cap or taperedportion 120 may include other shapes, such as, for example, a tip 123that is rounded, flat, square, hexagonal, or cylindroconical.

In some variations, the antenna assembly 12 includes a distal radiatingportion 105 and a proximal radiating portion 140. A junction member 130may be provided. Junction member 130, or portions thereof, may bedisposed between the proximal and distal radiating portions, 140 and105, respectively. In some embodiments, the distal and proximalradiating portions 105, 140 align at the junction member 130, which isgenerally made of a dielectric material, e.g., adhesives, and are alsosupported by the inner conductor that extends at least partially throughthe distal radiating portion 105. Junction member 130 may be formed fromany suitable elastomeric or ceramic dielectric material by any suitableprocess. In some embodiments, the junction member 130 is formed byover-molding and includes a thermoplastic elastomer, such as, forexample, polyether block amide (e.g., PEBAX®, manufactured by The ArkemaGroup of Colombes, France), polyetherimide (e.g., ULTEM® and/or EXTEM®,manufactured by SABIC Innovative Plastics of Saudi Arabia) and/orpolyimide-based polymer (e.g., VESPEL, manufactured by E.I. du Pont deNemours and Company of Wilmington, Del., United States). Junction member130 may be formed using any suitable over-molding compound by anysuitable process, and may include use of a ceramic substrate.

In some embodiments, the antenna assembly 12 may be provided with acoolant chamber (not shown). Additionally, the junction member 130 mayinclude coolant inflow and outflow ports (not shown) to facilitate theflow of coolant into, and out of, the coolant chamber. Examples ofcoolant chamber and coolant inflow and outflow port embodiments aredisclosed in commonly assigned U.S. patent application Ser. No.12/401,268 filed on Mar. 10, 2009, entitled “COOLED DIELECTRICALLYBUFFERED MICROWAVE DIPOLE ANTENNA”, now issued U.S. Pat. No. 8,118,808,and U.S. Pat. No. 7,311,703 entitled “DEVICES AND METHODS FOR COOLINGMICROWAVE ANTENNAS”.

In some embodiments, the antenna assembly 12 may be provided with anouter jacket (not shown) disposed about the distal radiating portion105, the junction 130 and/or the proximal radiating portion 140. Theouter jacket may be formed of any suitable material, such as, forexample, polymeric or ceramic materials. The outer jacket may be appliedby any suitable method, such as, for example, heat shrinking,over-molding, coating, spraying dipping, powder coating, baking and/orfilm deposition. The outer jacket may be a water-cooled catheter formedof a material having low electrical conductivity.

During microwave ablation, e.g., using the electrosurgical system 10,the probe 100 is inserted into or placed adjacent to tissue andmicrowave energy is supplied thereto. Ultrasound or computed tomography(CT) guidance may be used to accurately guide the probe 100 into thearea of tissue to be treated. Probe 100 may be placed percutaneously orsurgically, e.g., using conventional surgical techniques by surgicalstaff. A clinician may pre-determine the length of time that microwaveenergy is to be applied. Application duration may depend on many factorssuch as tumor size and location and whether the tumor was a secondary orprimary cancer. The duration of microwave energy application using theprobe 100 may depend on the progress of the heat distribution within thetissue area that is to be destroyed and/or the surrounding tissue.Single or multiple probes 100 may provide ablations in short proceduretimes, e.g., a few minutes, to destroy cancerous cells in the targettissue region.

A plurality of probes 100 may be placed in variously-arrangedconfigurations to substantially simultaneously ablate a target tissueregion, making faster procedures possible. Multiple probes 100 can beused to synergistically create a large ablation or to ablate separatesites simultaneously. Tissue ablation size and geometry is influenced bya variety of factors, such as the energy applicator design, number ofenergy applicators used simultaneously, time and wattage.

In operation, microwave energy having a wavelength, lambda (A), istransmitted through the antenna assembly 12, e.g., along the proximaland distal radiating portions 140, 105, and radiated into thesurrounding medium, e.g., tissue. The length of the antenna forefficient radiation may be dependent on the effective wavelengthλ_(eff), which is dependent upon the dielectric properties of the mediumbeing radiated. Antenna assembly 12 through which microwave energy istransmitted at a wavelength λ may have differing effective wavelengthsλ_(eff) depending upon the surrounding medium, e.g., liver tissue asopposed to breast tissue.

FIGS. 2 through 12 show a sequentially-illustrated, assembly ofcomponents forming an energy applicator or probe having a dielectricloaded aperture (e.g., “W” shown in FIG. 14), in accordance with thepresent disclosure. In FIG. 2, a coaxial feedline 226 is shown with theouter conductor 224 trimmed back, such that a portion 221 of thedielectric material 222 and the inner conductor 220 extends beyond theouter conductor 224. According to an embodiment of the presentdisclosure, an energy applicator or probe (shown generally as 200 inFIG. 2) includes an electrically conductive element 270 that extendsalong the longitudinal axis “A” of the energy applicator 200.Electrically conductive element 270 may be positioned in a distalportion of the probe 200. In some embodiments, theelectrically-conductive member 270 is a solid metal cylinder disposed atthe distal end of the portion 221 electrically coupled to the innerconductor 220 (e.g., by solder). Electrically conductive element 270 maybe formed of any suitable electrically-conductive material (e.g., metalsuch as stainless steel, aluminum, titanium, copper, etc.) of anysuitable length. The shape and size of the electrically conductiveelement 270 may be varied from the configuration depicted in FIG. 2.

FIG. 3 shows an energy applicator 300 according to an embodiment of thepresent disclosure that similar to the energy applicator 200 of FIG. 2,except for a dielectric layer 320 (also referred to herein as a baluninsulator) disposed coaxially about a distal portion of the outerconductor 224 of the feedline 226. Dielectric layer 320 may have asuitable length “L1” in a range from about 0.1 inches to about 3.0inches. The length “L1” may depend on the dielectric constant ofdielectric layer 320 and frequency. Dielectric layer 320 may be spacedapart from and disposed proximal to the distal end of the outerconductor 224. In some embodiments, the dielectric layer 320 is spacedapart, by a length “L2”, e.g., about 0.1 inches, from the distal end ofthe outer conductor 224. Balun insulator 320 may extend distally beyondthe distal end of the conductive balun sleeve (e.g., 430 shown in FIG.4) to direct current into a balancing/unbalancing (balun) structure(e.g., “B” shown in FIG. 4). Dielectric layer 320 may be formed of anysuitable insulative material, including, but not limited to, ceramics,water, mica, polyethylene, polyethylene terephthalate, polyimide,polytetrafluoroethylene (PTFE) (e.g., Teflon °, manufactured by E.I. duPont de Nemours and Company of Wilmington, Del., United States), glass,metal oxides or other suitable insulator, and may be formed in anysuitable manner. Dielectric layer 320 may be grown, deposited or formedby any other suitable technique. In some embodiments, the baluninsulator 320 is formed from a material with a dielectric constant inthe range of about 1.7 to about 10. The shape, size and relativeposition of the balun insulator 320 may be varied from the configurationdepicted in FIG. 3.

FIG. 4 shows an energy applicator 400 according to an embodiment of thepresent disclosure that is similar to the energy applicator 300 of FIG.3 except for an electrically-conductive layer 430 (also referred toherein as a conductive balun sleeve) disposed coaxially about a proximalportion of the energy applicator 400. Electrically-conductive layer 430may have any suitable length “L3”, e.g., about 0.1 inches to about 3.0inches. Length “L1” may depend on the dielectric constant of dielectriclayer 320 and frequency. Electrically-conductive layer 430 may be formedas a single structure and electrically coupled to the outer conductor224, e.g., by solder or other suitable electrical connection. In someembodiments, the electrically-conductive layer 430 includes a firstportion 431, having a length “L5”, disposed coaxially about a proximalportion of the dielectric layer 320, and a second portion 432, having alength “L4”, disposed proximally to the first portion 431 electricallycoupled to the outer conductor 224. First and second portions 431, 432may be formed of any suitable electrically-conductive material, e.g.,metal such as stainless steel, titanium, copper, etc., and may be formedin any suitable manner. First and second portions 431, 432 may be formedseparately from each other. First and second portions 431, 432 may forma single, unitary structure. The shape and size of theelectrically-conductive balun sleeve 430 may be varied from theconfiguration depicted in FIG. 4.

FIG. 5 shows an energy applicator 500 according to an embodiment of thepresent disclosure that is similar to the energy applicator 400 of FIG.4, except for an electrically-conductive cylinder 540 disposed coaxiallyabout a distal portion of the electrically-conductive layer 430.Electrically-conductive cylinder 540 may have a suitable length “L6” ofa range from about 0.05 inches to about 0.2 inches. For example, thelength “L6” may be selected to provide mechanical stability. In someembodiments, the distal edge of electrically-conductive cylinder 540 isdisposed overlying the distal edge of the electrically-conductive layer430. The shape and size of the electrically-conductive cylinder 540 maybe varied from the configuration depicted in FIG. 5.

FIG. 6 shows an energy applicator 600 according to an embodiment of thepresent disclosure that includes an electrically-conductive layer 630and an electrically-conductive cylinder 640. Electrically-conductivelayer 630 surrounds a proximal portion of the dielectric layer 320 andis electrically coupled to the outer conductor 224, e.g., by solder orother suitable electrical connection. Electrically-conductive layer 630is similar to the electrically-conductive layer 430 of FIG. 4, exceptthat the electrically-conductive layer 630 has a length that is lessthan the length “L3” of the electrically-conductive layer 430. As shownin FIG. 6, the electrically-conductive layer 630 may have a length “L7”,which is shorter than the length “L3” by a length “L9”.

Electrically-conductive cylinder 640 shown in FIGS. 6 and 7 is similarto the electrically-conductive cylinder 540 of FIG. 5, except that theelectrically-conductive cylinder 640 extends distally beyond the distaledge of the electrically-conductive layer 630. As shown in FIG. 7, theelectrically-conductive cylinder 640, having a length “L6”, includes afirst portion 641, having a length “L8”, disposed coaxially about thedistal end of the electrically-conductive layer 630, and a secondportion 642, having a length “L9”, disposed distally to the firstportion 641, surrounding a portion of the dielectric layer 320 distallyextending beyond the electrically-conductive layer 630. In someembodiments, the electrically-conductive cylinder 640 is positionedrelative to the distal edge of the electrically-conductive layer 630such that the combined length of the electrically-conductive layer 630and the electrically-conductive cylinder 640 is a length “L3”, which maybe, for example, a quarter wavelength or a half wavelength. The shapeand size of the electrically-conductive cylinder 640 may be varied fromthe configuration depicted in FIGS. 6 and 7.

FIG. 8 shows an energy applicator 800 according to an embodiment of thepresent disclosure that is similar to the energy applicator 500 of FIG.5, except for a generally longitudinally-disposed dielectric structure850. In some embodiments, the dielectric structure 850 includes adielectric cap configured to cover the distal end of theelectrically-conductive member 270. As shown in FIG. 8, the dielectricstructure 850 may be disposed distally to the electrically-conductivecylinder 540. Dielectric structure 850 may be formed using over-moldingtechniques or other forming techniques. In some embodiments, thedielectric structure 850 is formed from a material with a dielectricconstant in the range of about 1.7 to about 10. The shape and size ofthe dielectric structure 850 may be varied from the configurationdepicted in FIG. 8.

In some embodiments, the dielectric structure 850 includes a firstdielectric segment 851, a second dielectric segment 852, and a thirddielectric segment 853. As shown in FIG. 8, the first dielectric segment851 extends distally from the distal end of the electrically-conductivecylinder 540 and may have a substantially half-cylindrical shape. Firstdielectric segment 851 may be made to encompass any radial angle. Insome embodiments, the first dielectric segment 851 extends from thedistal end of the electrically-conductive cylinder 540 to distal end ofthe electrically-conductive member 270. Second dielectric segment 852 isconfigured to cover the distal end of the electrically-conductive member270. In some embodiments, the first and second dielectric segments 851,852 are integrally formed in a molding process. First dielectric segment851, the second dielectric segment 852 and the third dielectric segment853 may each be formed by any suitable process.

FIG. 9 shows an energy applicator 900 according to an embodiment of thepresent disclosure that is similar to the energy applicator 800 of FIG.8, except for a longitudinally-extending inflow tube 961, alongitudinally-extending outflow tube 962, and anelectrically-conductive cylinder 940 having a notch “N” defined thereinthat is configured to receive the inflow and outflow tubes 961, 962. Insome embodiments, the inflow and outflow tubes 961, 962 are configuredto supply and/or dispense coolant fluid (e.g., saline, water or othersuitable coolant fluid) into and out of a distal portion of a coolingchamber (e.g., 1390 shown in FIG. 13). A pump (not shown) may beconnected in fluid communication between the cooling chamber and acoolant source (e.g., 18 shown in FIG. 1). Inflow and outflow tubes 961,962 may include thin-walled polyimide tubes. In some embodiments, a pump(not shown) supplies coolant fluid from a coolant source (e.g., 18 shownin FIG. 1) to one or more inflow tubes 961 which, in turn, delivercoolant fluid (e.g., “F” shown in FIG. 13B) to the cooling chamber(e.g., 1391 shown in FIG. 13B). Additionally, or alternatively, a pumpmay be fluidly coupled to one or more outflow tubes 962 to draw coolantfluid out of the cooling chamber.

As shown in FIGS. 9 and 10, the inflow and outflow tubes 961, 962 mayextend longitudinally across the full length of theelectrically-conductive layer 430 and at least partially across thedielectric structure 850. As shown in FIG. 10, a portion or segment “S”of the inflow and outflow tubes 961, 962 is disposed within a notch “N”defined within the electrically-conductive cylinder 940. In someembodiments, the notch “N” is configured as a recess, e.g., in the formof a groove or hole. In other embodiments, the notch “N” is configuredas a first recess (not shown) and a second recess (not shown), whereinthe first recess is configured to receive one or more inflow tubes 961and the second recess is configured to receive one or more outflow tubes962. Inflow tube 961 and the outflow tube 962 may be formed to have thesame diameters or different diameters. Inflow and outflow tubes 961, 962may have any suitable length. In some embodiments, the segment “S” ofthe inflow and outflow tubes 961, 962 is disposed between theelectrically-conductive layer 430 and the outer circumferential surfaceof the electrically-conductive cylinder 940, which helps minimize theouter diameter of the device. Inflow and outflow tubes 961, 962 may beheld in place, e.g., along the electrically-conductive layer 430 and/orwithin the notch “N”, by using UV adhesive or other similar suitableadhesives, as well as heat shrink tubing or by other suitable methods.The shape and size of the inflow and outflow tubes 961, 962, theelectrically-conductive cylinder 940 and the notch “N” may be variedfrom the configurations depicted in FIGS. 9 and 10.

FIG. 11A shows an energy applicator 1100 according to an embodiment ofthe present disclosure that is similar to the energy applicator 800 ofFIG. 8, except for a sleeve member 1160. Sleeve member 1160 may be anelongated tubular body of a catheter assembly. As shown in FIG. 11A, thesleeve member 1160 may include a first sleeve portion 1163 and a secondsleeve portion 1165 disposed distally to the first sleeve portion 1163.First sleeve portion 1163 may be configured to coaxially surround aproximal portion of the energy applicator 1100. Second sleeve portion1165 may be configured to partially surround a distal portion of theenergy applicator 1100. In some embodiments, the first sleeve portion1163 has a substantially cylindrical shape, and the second sleeveportion 1165 has a substantially half-cylindrical shape. According to anembodiment of the present disclosure, an opening or electromagnetic“window” shown generally as “W” in FIGS. 12A through 14 is partiallydefined by the longitudinal edges of the second sleeve portion 1165.Second sleeve portion 1165 may include an engagement portion “P”, whichextends beyond the distal end of the dielectric structure 850.

Sleeve member 1160 may be formed of a suitable electrically conductivematerial such as metal or polymeric material. A suitable metal mayinclude, for example, stainless steel, titanium, titanium alloys such asnickel-titanium and titanium-aluminum-vanadium alloys, aluminum,aluminum alloys, tungsten carbide alloys or combinations thereof. Asuitable polymeric material may include, for example, thermoplasticsincluding reinforced or unreinforced polymers, e.g., polyamide (nylon)or polyaramid (e.g., KEVLAR® manufactured by E.I. du Pont de Nemours andCompany of Wilmington, Del., United States), or any suitable polymericcomposite, e.g., polymers filled with carbon particles, silica,conductive particles such as metal particles or conductive polymers, orcombinations thereof.

FIG. 11B shows an energy applicator 1101 according to an embodiment ofthe present disclosure that is similar to the energy applicator 900 ofFIG. 9, except for a sleeve member 1161. Energy applicator 1101 includesthe inflow and outflow tubes 961, 962 shown in FIGS. 9 and 10. As shownin FIG. 11B, the sleeve member 1161 may include a first sleeve portion1164 and a second sleeve portion 1166 disposed distally to the firstsleeve portion 1164. Portions of the inflow and outflow tubes 961, 962disposed proximal to the electrically-conductive cylinder 940 arecovered by the first sleeve portion 1164. Sleeve member 1161 is similarto the sleeve member 1160 shown in FIG. 11A, and further descriptionthereof is omitted in the interests of brevity.

FIG. 12A shows an energy applicator 1200 according to an embodiment ofthe present disclosure that is similar to the energy applicator 1100 ofFIG. 11A, except for an end member 1240. End member 1240, or portionsthereof, may be formed of a suitable non-conductive material, such as,for example, ULTEM®. End member 1240, or portions thereof, may be formedof a suitable conductive material such as metal, e.g., stainless steel.End member 1240 may include one or more conductive materials and/or oneor more non-conductive materials. In some embodiments, the end member1240 includes a shoulder portion 1244 having a generally cylindricalshape having a proximal end and a distal end. Shoulder portion 1244 maybe configured to engage an engagement portion (e.g., “P” shown in FIGS.11A and 12A) disposed at the distal end of the sleeve member 1160. Theshape and size of the shoulder portion 1244 may be varied from theconfiguration depicted in FIG. 12A.

In some embodiments, the end member 1240 includes a central portion 1247having a generally cylindrical shape having a proximal end and a distalend, wherein the proximal end of the central portion 1247 is coupled tothe distal end of the shoulder portion 1244. Additionally, oralternatively, the end member 1240 may include a tapered portion 1230extending distally from the distal end of the central portion 1247.Tapered portion 1230 may terminate in a sharp tip 1231 to allow forinsertion into tissue with minimal resistance. In those cases where theenergy applicator is inserted into a pre-existing opening, the tip 1231may be rounded or flat. The shape and size of the central portion 1247and tapered portion 1230 may be varied from the configuration depictedin FIG. 12A.

FIG. 12B shows an energy applicator 1201 according to an embodiment ofthe present disclosure that is similar to the energy applicator 1101 ofFIG. 11B, except for an end member 1241. End member 1241 is similar tothe end member 1240 shown in FIG. 12A, and further description thereofis omitted in the interests of brevity.

FIG. 13A shows an energy applicator 1300 according to an embodiment ofthe present disclosure that is similar to the energy applicator 1200 ofFIG. 12A, except for a generally longitudinally-disposed dielectricmember 1390. Dielectric member 1390 may be formed of an insulatingmaterial, such as, for example, a polyimide or similar dielectricmaterial, to avoid shielding microwave radiation around the antennaassembly. Dielectric member 1390 may be formed over a portion of thedielectric structure 850 by a suitable molding process.

FIG. 13B shows an energy applicator 1301 according to an embodiment ofthe present disclosure that is similar to the energy applicator 1201 ofFIG. 12B, except for a generally longitudinally-disposed chamber 1391(also referred to herein as a cooling chamber). Energy applicator 1301includes one or more inflow tubes 961 and one or more outflow tubes 962.Portions of the inflow and outflow tubes 961, 962 are disposed withinthe cooling chamber 1391, as shown in phantom lines in FIG. 13B. Inflowand outflow tubes 961, 962 are configured to supply and/or dispensecoolant fluid “F” (e.g., saline, water or other suitable coolant fluid)into and out of a distal portion of the cooling chamber 1391. Coolingchamber 1391 may be disposed at least partially about anelectrically-conductive member (e.g., 270 shown in FIG. 6). The shapeand size of the inflow and outflow tubes 961, 962 and the coolingchamber 1391 may be varied from the configuration depicted in FIG. 13B.

FIG. 14 shows an energy applicator 1400 according to an embodiment ofthe present disclosure that is similar to the energy applicator 1300 ofFIG. 13A, except for a material 1420 disposed over the dielectric member1390. Material 1420 may be deposited in an over-molding process.Material 1420 may be a nonconductive radio frequency transparentmaterial, e.g., a glass fiber epoxy composite or polyimide. In someembodiments, the dielectric materials filling the coaxial structure atthe site of the opening “W” may vary in dielectric constant with shellsor more complex dielectric layering to achieve the optimum antennadirectivity and energy to tissue delivery.

Energy applicator 1400 may include an indicia alignment mark (not shown)such as a colored strip or the like, e.g., to provide a visual cue tothe surgeon to allow orientation of the direction of flow of the energyto coincide with the indicia alignment mark. Additionally, oralternatively, the energy applicator 1400 may include indicia graduationmarks (not shown) for insertion depth reference, e.g., to indicate theposition of the opening (e.g., “W” shown in FIG. 17) relative to thesurface of the tissue “T”. Examples of indicia alignment mark and theindicia graduation mark embodiments are disclosed in commonly assignedU.S. patent application Ser. No. 12/476,960 filed on Jun. 2, 2009,entitled “ELECTROSURGICAL DEVICES WITH DIRECTIONAL RADIATION PATTERN”.

The outer surface of the energy applicator 1400 may be coated with asuitable lubricious substance, such as TEFLON®, to aid in the movementof the energy applicator 1400 in or through tissue as well as to aid inpreventing tissue from sticking to the outer surface of the device.

FIGS. 15 and 16 show a cross section of an energy applicator (e.g., 1400shown in FIG. 14) according to an embodiment of the present disclosurethat may be suitable for use in tissue ablation applications. FIGS. 15and 16 show examples of directional radiation patterns emitted by theenergy applicator 1400 according to embodiments of the presentdisclosure.

FIG. 17 shows an embodiment of an energy applicator (e.g., 1400 shown inFIG. 14) coupled to a transmission line 15 according to the presentdisclosure. Transmission line 15 may connect the energy applicator 1400to a power generating source, e.g., a microwave or RF electrosurgicalgenerator. During a procedure, e.g. an ablation procedure, the energyapplicator 1400 is inserted into or placed adjacent to tissue “T” andenergy is supplied thereto. Energy applicator 1400 may be placedpercutaneously or atop tissue. Ultrasound or computed tomography (CT)guidance may be used to accurately guide the energy applicator 1400 intothe area of tissue “T” to be treated. Energy applicator 1400 may berotatable about a longitudinal axis “A-A” (shown in FIG. 2) such thatthe directional radiation pattern “R” rotates therewith. Examples ofantenna assemblies rotatable about axis “A-A” such that any elongatedradiation lobes rotates therewith are disclosed in commonly assignedU.S. patent application Ser. No. 12/197,405 filed on Aug. 25, 2008,entitled “MICROWAVE ANTENNA ASSEMBLY HAVING A DIELECTRIC BODY PORTIONWITH RADIAL PARTITIONS OF DIELECTRIC MATERIAL”, now issued U.S. Pat. No.8,211,098.

FIGS. 18 through 20 show various configurations of dielectric materialat the site of an opening or electromagnetic “window” (e.g., “W” shownin FIG. 17) of an energy applicator (e.g., 1400 shown in FIG. 17) andexamples of emitted directional radiation patterns, according toembodiments of the present disclosure.

FIG. 18 shows a cross-sectional view of an energy applicator 1800 and anemitted radiation pattern “R1” of microwave energy radiated therefrom.In FIG. 18, the window is approximately ½ the circumference of thesleeve member 1893 thereof. A first dielectric structure 1864 and asecond dielectric structure 1862 are coupled to an inner conductor 270at the site of the window. Inner conductor 270 may be similar to theinner conductor 220 shown in FIG. 2. First and second dielectricstructures 1864, 1862 may have substantially the same diameter. Seconddielectric structure 1862 may be similar to the first dielectric segment851 shown in FIG. 8. In the embodiment depicted in FIG. 18, the sleevemember 1893 extends over the second dielectric structure 1862. Thewindow in the sleeve member is filled with a radio frequency (RF)transparent material 1885, e.g., a glass fiber epoxy composite orpolyimide.

FIG. 19 shows a cross-sectional view of an energy applicator 1900 and anemitted radiation pattern “R2” of microwave energy radiated therefrom.In the energy applicator 1900, the window is approximately ¼ thecircumference of the sleeve member 1993 thereof. A first dielectricstructure 1964 and a second dielectric structure 1962 are coupled to theinner conductor 270 at the site of the window. In the embodimentdepicted in FIG. 19, the sleeve member 1993 extends fully over thesecond dielectric structure 1962 and partially over the first dielectricstructure 1964. The window in the sleeve member 1993 of the energyapplicator 1900 is filled with a RF transparent material 1985.

FIG. 20 shows a cross-sectional view of an energy applicator 2000 and anemitted radiation pattern “R3” of microwave energy radiated therefrom.In the energy applicator 2000, the window is approximately ⅘ thecircumference of the sleeve member 2093. A first dielectric structure2064 and a second dielectric structure 2062 are coupled to the innerconductor 270 at the site of the window. In the embodiment depicted inFIG. 20, the window and the RF transparent material 2085 disposedtherein extends fully over the first dielectric structure 2064 andpartially over the second dielectric structure 2062.

Hereinafter, a method of manufacturing an energy applicator or probehaving a dielectric loaded coaxial aperture with distally positionedresonant structure, in accordance with the present disclosure, isdescribed with reference to FIG. 21. It is to be understood that thesteps of the method provided herein may be performed in combination andin a different order than presented herein without departing from thescope of the disclosure.

FIG. 21 is a flowchart illustrating a method of manufacturing anelectrosurgical device according to an embodiment of the presentdisclosure. In step 2110, a coaxial feedline (e.g., 226 shown in FIG. 2)is provided. The coaxial feedline includes an inner conductor (e.g., 220shown in FIG. 2), an outer conductor (e.g., 224 shown in FIG. 2), and adielectric material (e.g., 222 shown in FIG. 2) disposed therebetween. Aportion of the inner conductor and the dielectric material (e.g., 221shown in FIG. 2) may extend beyond the outer conductor at the distal endof the coaxial feedline.

In step 2120, an elongated electrically-conductive member (e.g., 270shown in FIG. 2) is joined to the distal end of the inner conductor(e.g., 220 shown in FIG. 2) at a distal end of the coaxial feedline. Insome embodiments, the electrically-conductive member is a solid metalcylinder electrically coupled to the inner conductor, e.g., by solder orother suitable electrical connection.

In step 2130, a dielectric layer (e.g., 320 shown in FIG. 3) is joinedto a distal portion of the outer conductor (e.g., 224 shown in FIG. 3).In some embodiments, the dielectric layer is spaced apart from anddisposed proximal to the distal end of the outer conductor.

In step 2140, an electrically-conductive layer (e.g., 430 shown in FIG.4) is joined to a proximal portion of the dielectric layer (e.g., 320shown in FIG. 4). In some embodiments, a portion of the dielectric layerextends distally beyond the electrically-conductive layer, e.g., todirect current into a coaxial choke network or balun structure.

In step 2150, the electrically-conductive layer is coupled to the outerconductor of the coaxial feedline. In some embodiments, theelectrically-conductive layer includes a first portion (e.g., 431 shownin FIG. 4) disposed coaxially about a proximal portion of the dielectriclayer, and a second portion (e.g., 432 shown in FIG. 4) disposedproximally to the first portion, the second portion electrically coupledto the outer conductor.

In step 2160, an electrically-conductive cylinder (e.g., 540 shown inFIG. 5) is positioned overlying a distal portion of theelectrically-conductive layer (e.g., 430 shown in FIG. 5). In someembodiments, a portion (e.g., 642 shown in FIG. 7) of theelectrically-conductive cylinder (e.g., 640 shown in FIGS. 6 and 7)extends distally beyond the distal edge of the electrically-conductivelayer (e.g., 630 shown in FIG. 7). In some embodiments, theelectrically-conductive cylinder is positioned relative to the distaledge of the electrically-conductive layer such that the combined lengthof the electrically-conductive layer and the electrically-conductivecylinder is a quarter wavelength or a half wavelength.

In step 2170, a dielectric structure (e.g., 850 shown in FIG. 8) isformed having a proximal end disposed substantially adjacent to a distalend of the electrically-conductive cylinder, wherein the dielectricstructure longitudinally extends from the distal end of theelectrically-conductive cylinder to a distal end of theelectrically-conductive member. In some embodiments, the dielectricstructure includes a dielectric cap (e.g., 852 shown in FIG. 8)configured to cover the distal end of the electrically-conductivemember. The dielectric structure may be formed using over-moldingtechniques or other forming techniques.

The above-described electrosurgical devices for treating tissue andmethods of directing electromagnetic radiation to a target volume oftissue may be used to provide directional microwave ablation, whereinthe heating zone may be focused to one side of the electrosurgicaldevice, thereby allowing clinicians to target small and/or hard toaccess tumors without having to penetrate the tumor directly or killmore healthy tissue than necessary. The presently disclosedelectrosurgical devices may allow clinicians to avoid ablating criticalstructures, such as large vessels, healthy organs or vital membranebarriers, by placing the electrosurgical device between the tumor andcritical structure and directing the electromagnetic radiation towardthe tumor and away from the critical structure.

Although embodiments have been described in detail with reference to theaccompanying drawings for the purpose of illustration and description,it is to be understood that the inventive processes and apparatus arenot to be construed as limited thereby. It will be apparent to those ofordinary skill in the art that various modifications to the foregoingembodiments may be made without departing from the scope of thedisclosure.

What is claimed is:
 1. An electrosurgical device for directing energy toa target volume of tissue, comprising: a coaxial feedline having aninner conductor, an outer conductor coaxially disposed around the innerconductor, and a dielectric material disposed therebetween; an elongatedelectrically-conductive member longitudinally disposed at a distal endof the inner conductor; a balun including: a dielectric layer coaxiallydisposed around a distal portion of the outer conductor of the feedline;and an electrically-conductive layer coaxially disposed around at leasta proximal portion of the dielectric layer; an electrically-conductivecylinder including a first portion coaxially disposed around a distalportion of the electrically-conductive layer of the balun and a secondportion disposed distally to the first portion, wherein the secondportion distally extends beyond a distal end of theelectrically-conductive layer of the balun; and a dielectric structuredisposed substantially adjacent to a distal end of theelectrically-conductive cylinder, wherein the dielectric structurelongitudinally extends from the distal end of theelectrically-conductive cylinder to a distal end of theelectrically-conductive member.
 2. The electrosurgical device of claim1, wherein a portion of the inner conductor and the dielectric materialof the coaxial feedline extends beyond the outer conductor at a distalend of the coaxial feedline.
 3. The electrosurgical device of claim 1,wherein the electrically-conductive member is electrically coupled tothe inner conductor.
 4. The electrosurgical device of claim 1, whereinthe balun is a quarter-wave sleeve.
 5. The electrosurgical device ofclaim 1, wherein the electrically-conductive layer includes a firstportion coaxially disposed around the proximal portion of the dielectriclayer, and a second portion disposed proximally to the first portion,the second portion electrically coupled to the outer conductor.
 6. Theelectrosurgical device of claim 1, wherein the dielectric structure isconfigured to cover a distal end of the electrically-conductive member.7. The electrosurgical device of claim 1, further comprising: a coolingchamber disposed at least partially about the electrically-conductivemember.
 8. The electrosurgical device of claim 7, further comprising: aninflow tube configured to supply a coolant fluid into the coolingchamber; and an outflow tube configured to dispense the coolant fluidfrom the cooling chamber.
 9. The electrosurgical device of claim 8,further comprising: a coolant source to supply the coolant fluid. 10.The electrosurgical device of claim 1, further comprising: a sleevemember including a first sleeve portion and a second sleeve portion, thesecond sleeve portion disposed distally to the first sleeve portion,wherein the first sleeve portion is disposed proximal to the dielectricstructure and the second sleeve portion is configured to partiallysurround the dielectric structure.
 11. The electrosurgical device ofclaim 10, further comprising an electromagnetic window configured toemit a directional radiation pattern in operation.
 12. Theelectrosurgical device of claim 11, wherein the electromagnetic windowis partially defined by longitudinal edges of the second sleeve portion.13. The electrosurgical device of claim 11, wherein the electromagneticwindow includes a radio frequency (RF) transparent material.
 14. Theelectrosurgical device of claim 10, wherein the second sleeve portionincludes an engagement portion extending beyond a distal end of thedielectric structure.
 15. The electrosurgical device of claim 1, furthercomprising a tapered portion having a tip configured to penetratetissue.
 16. A method of manufacturing an electrosurgical device,comprising the steps of: providing a coaxial feedline having an innerconductor, an outer conductor, and a dielectric material disposedtherebetween; joining an electrically-conductive member to a distal endof the inner conductor at a distal end of the coaxial feedline; forminga dielectric layer around a distal portion of the outer conductor;forming an electrically-conductive layer around a proximal portion ofthe dielectric layer such that the electrically-conductive layer iselectrically coupled to the outer conductor; joining a first portion ofan electrically-conductive cylinder to a distal portion of theelectrically-conductive layer, a second portion of theelectrically-conductive cylinder distally extending beyond a distal endof the electrically-conductive laver; and forming a dielectric structuredisposed substantially adjacent to a distal end of theelectrically-conductive cylinder, wherein the dielectric structurelongitudinally extends from the distal end of theelectrically-conductive cylinder to a distal end of theelectrically-conductive member.
 17. The method of manufacturing anelectrosurgical device in accordance with claim 16, wherein thedielectric structure includes a cap of dielectric material configured tocover a distal end of the electrically-conductive member.
 18. The methodof manufacturing an electrosurgical device in accordance with claim 16,further comprising the step of: joining a sleeve member to theelectrically-conductive cylinder, the sleeve member configured topartially surround the dielectric structure.
 19. The electrosurgicaldevice of claim 1, wherein the electrically-conductive layer of thebalun has a length and the second portion of the electrically-conductivecylinder has a length, and wherein a combined length of the length ofthe electrically-conductive layer of the balun and the length of thesecond portion of the electrically-conductive cylinder is a quarterwavelength.